易百教程

Deque是一个更精简的元素集合，支持两端元素的插入和删除。 它发音为’双端队列’。 Deque接口提供了插入，删除和检查队列两端元素的方法。 这些方法是：

• addFirst()，offerFirst()和push() - 将元素插入双端队列的头部。
• add()，addLast()，offerLast()和offer() - 将元素插入双端队列的尾部。
• element()，getFirst()，peek()和peekFirst() - 从双端队列的头部检索元素。
• getLast()和peekLast() - 从双端队列的尾部检索元素。
• remove()，removeFirst()，poll()，pollFirst()和pop() - 从双端队列中删除元素。
• removeLast()和pollLast() - 从双端队列的尾部删除元素。

ArrayDeque和LinkedList是Collection API中Deque接口的实现。

文件：DequeExample.java -

package com.yiibai.tutorial;

import java.util.Deque;
import java.util.LinkedList;

/**
 * @author yiibai
 *
 */
public class DequeExample {
    public static void main(String[] args) {
        Deque<String> deque=new LinkedList<>();
        /*Adding element to deque*/
        deque.add("One");
        deque.addFirst("Two");
        deque.addLast("Three");
        deque.offer("Four");
        deque.offerFirst("Five");
        deque.offerLast("Six");
        deque.push("Seven");


        System.out.println("Elements in deque: "+deque);
        System.out.println();

        /*Retrieving elements from deque*/
        System.out.println("element() : "+deque.element());
        System.out.println("getFirst() : "+deque.getFirst());
        System.out.println("getLast() : "+deque.getLast());
        System.out.println("peek() : "+deque.peek());
        System.out.println("peekFirst() : "+deque.peekFirst());
        System.out.println("peekLast() : "+deque.peekLast());

        /*Removing elements from deque */
        System.out.println();

        System.out.println("remove() : "+deque.remove());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("removeFirst() : "+deque.removeFirst());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("removeLast() : "+deque.removeLast());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("poll() : "+deque.poll());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("pollFirst() : "+deque.pollFirst());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("pollLast() : "+deque.pollLast());
        System.out.println("Elements in deque after removal : "+deque);

        System.out.println("pop() : "+deque.pop());
        System.out.println("Elements in deque after removal : "+deque);
    }
}

执行上面示例代码，得到以下结果：

Elements in deque: [Seven Five Two One Three Four Six]

element() : Seven
getFirst() : Seven
getLast() : Six
peek() : Seven
peekFirst() : Seven
peekLast() : Six

remove() : Seven
Elements in deque after removal : [Five Two One Three Four Six]
removeFirst() : Five
Elements in deque after removal : [Two One Three Four Six]
removeLast() : Six
Elements in deque after removal : [Two One Three Four]
poll() : Two
Elements in deque after removal : [One Three Four]
pollFirst() : One
Elements in deque after removal : [Three Four]
pollLast() : Four
Elements in deque after removal : [Three]
pop() : Three
Elements in deque after removal : []